ARM: dts: ux500: Add "simple-bus" compatible to soc node

The "soc" node in the Ux500 device tree does not need any special
handling - it is just a simple I/O bus that can be accessed without
additional configuration.

Therefore we can additionally describe it as compatible with "simple-bus".
This can be used by platforms to probe devices under the soc node without
special handling for our custom "stericsson,db8500" compatible
(e.g. in U-Boot).

Signed-off-by: Stephan Gerhold <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

arch/arm/boot/dts/ste-dbx5x0.dtsi

···
 	soc {
 		#address-cells = <1>;
 		#size-cells = <1>;
-		compatible = "stericsson,db8500";
+		compatible = "stericsson,db8500", "simple-bus";
 		interrupt-parent = <&intc>;
 		ranges;